Typically, long travel sootblowers are equipped with two support rollers located at the front or boiler end of the sootblower (see for example U.S. Pat. No. 3,585,673, granted June 22, 1971). The function of these rollers is to support the lance tube in a vertical plane and to control and limit its lateral motion in a horizontal plane. With the sootblower in its fully retracted position, only a short length of the lance tube extends beyond the front rollers toward the boiler, and the lance tube is then supported at its back end by the carriage and near its front end by the front support rollers. In this position, the load on the front rollers is at a minimum. As the carriage is moved forward, thus projecting the lance tube into the boiler, the load on the front rollers steadily increases until with the lance tube fully extended the load is maximum.
As the lance tube progresses from the fully retracted to the fully extended position the radius of curvature of that portion of the lance tube which is bearing on the front rollers is constantly changing as is the location of the center of the radius of curvature, both in a vertical and horizontal plane.
With the increasing size of boilers it has been necessary to construct sootblowers having longer and longer travel, some lance tubes being required to extend into a boiler distances exceeding 50 feet. As a result of such increased lance tube weight and the heavy overbalanced loads developed by the lance tubes of such blowers when extended, front roller assemblies are required to carry extreme loads, and the stresses applied to the rollers, bearings and supporting structure, as well as to the lance tube itself and the lance tube driving mechanism, have become very high. It will be recognized that such stresses affect the weight and power factors that must be taken into account in the design of the equipment, and/or the life of the components. While it is possible to somewhat increase the front roller diameters to reduce stresses, the lance tube diameter cannot easily be increased.
The present invention has as its primary objective the provision of an improved multiple roller front supporting structure which greatly reduces the stress concentrations imposed upon the lance tube, rollers and associated parts, which distributes the loads imposed upon the lance tube and which is so designed that the loads are equalized on all of the rollers. A further object is to provide such a construction which maintains uniform distributed loading of the lance tube, rollers and other parts even though the lance tube may have become distorted.
Still another object is to provide such a construction wherein changes in the frictional loads imposed by the rollers and bearings do not affect the uniformity of weight loading imposed by the lance tube on the several rollers.
Other objects and advantages will become apparent upon consideration of the present disclosure in its entirety.